The present invention relates to a joint driving apparatus for generating a relative movement between first and second members on a joint.
In a prior art joint driving apparatus, a rotational motor is used to generate a relative movement between first and second members on a joint. In another prior art joint driving apparatus, a linear motor is used to generate the relative movement between first and second members on the joint, and a stator structure of the linear motor is similar to that of the rotational motor.
An object of the present invention is to provide a joint driving apparatus for generating a relative movement between first and second members on a joint, by which apparatus a magnetic flux is effectively utilized to generate a force for urging the first and second members with respect to each other.
According to the invention, in a joint driving apparatus for generating a relative movement between first and second members on a joint, comprising, a linear motor including at least one stator part fixed to another one of the first and second members, a movable element movable with respect to the stator part in a movable direction and connected to the one of the first and second members to be moved with respect to the another one of the first and second members, and an electromagnetic coil device for energizing the stator part to be magnetized so that a magnetic field for urging the movable element in the movable direction with respect to the stator part is generated, the stator part includes at least two pairs of magnetic poles, the at least two pairs are adjacent to each other in the movable direction, the magnetic poles of each of the at least two pairs face to each other through the movable element in a traverse direction perpendicular to the movable direction to generate the magnetic field passing the magnetic poles through the movable element, and a magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction when the stator part is magnetized.
Since the magnetic poles of each of the at least two pairs face to each other through the movable element in a traverse direction perpendicular to the movable direction to generate the magnetic field passing the magnetic poles through the movable element, and a magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction when the stator part is magnetized, a magnetic flux is effectively utilized to generate a force for urging the first and second members with respect to each other.
The joint driving apparatus may further comprise a sensor for generating a signal corresponding to an actual movement of the movable element with respect to the stator part, wherein the electromagnetic coil device controls a change in energized phase of the stator part on the basis of a comparison between the signal and an instructed movement of the movable element with respect to the stator parts to form a closed-loop control system. The electromagnetic coil device may control a change in energized phase of the stator part on the basis of an instructed movement of the movable element with respect to the stator part to form an open-loop control system. An actual movement of the movable element with respect to the stator part may be estimated from a voltage induced in the electromagnetic coil device by the actual movement of the movable element or from an electric current flowing through the electromagnetic coil device.
When the apparatus comprises at least two of the stator parts, the electromagnetic coil device energizes the at least two stator parts respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, P is a pitch of the pairs of the magnetic poles adjacent to each other in the movable direction in each of the stator parts, k is an integral number not less than zero, and M is a number of the stator parts energized with respective energized phases different from each other while M is an integral number not less than two, a distance between the pair of magnetic poles of one of the stator parts and the pair of magnetic poles of another one of the stator parts adjacent to each other in the movable direction=(k*P)+(P/M).
The joint driving apparatus may further comprise an elastic member a part of which is connected to one of the first and second members, wherein the movable element is connected to another part of the elastic member to drive the one of the first and second members through the elastic member with respect to the another one of the first and second members. The apparatus may comprise a plurality of pairs of the elastic members and linear motors while the relative movement between the first and second members is performed along each of directions different from each other by respective one of the pairs of the elastic members and linear motors. The apparatus may comprise a plurality of the elastic members while the relative movement between the first and second members is performed along each of directions different from each other by respective one of the elastic members connected selectively to the linear motor. The joint driving apparatus may further comprise a dust cover covering a portion of the movable element projecting from the stator parts. The joint driving apparatus may further comprise a cooling device for cooling the linear motor. The joint driving apparatus may further comprise a switching device for switching, between a battery and an outer electric power source, an electric power supply source for supplying an electric power to the linear motor. The joint driving may further comprise a spring member for urging the movable element with respect to the another one of the first and second members in the movable direction. The elastic member may include a spring for connecting elastically between the movable element and the one of the first and second members. The elastic member may include a rubber for connecting elastically between the movable element and the one of the first and second members.
When first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, second one of the magnetic poles of each of the at least two pairs faces to a second side surface of the movable element opposite to the first side surface in the traverse direction, a magnetic polar direction between the first one of the magnetic poles of one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs is opposite to a magnetic polar direction between the first one of the magnetic poles of another one of the at least two pairs and the second one of the magnetic poles of the another one of the at least two pairs, and the at least two pairs is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized.
When first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, second one of the magnetic poles of each of the at least two pairs faces to a second side surface of the movable element opposite to the first side surface in the traverse direction, the stator part has a magnetic core and the electromagnetic coil device has an electromagnetic coil surrounding an intermediate portion of the magnetic core between longitudinal ends of the magnetic core to generate a magnetic field passing the longitudinal ends of the magnetic core so that the at least two pairs of magnetic poles are energized by the electromagnetic coil, and one of the longitudinal ends of the magnetic core forms both of the first one of the magnetic poles of the one of the at least two pairs and the second one of the magnetic poles of the another one of the at least two pairs while another one of the longitudinal ends of the magnetic core forms both of the first one of the magnetic poles of the another one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs, a size of the magnetic core is minimized.
When the apparatus comprises at least two of the stator parts energized respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, and each of the stator parts is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized.
When the apparatus comprises at least two of the stator parts energized respectively to be magnetized with a difference in energized phase between the at least two stator parts so that a travelling magnetic field for urging the movable element in the movable direction is generated by a cooperation between the at least two stator parts, and the at least two pairs of magnetic poles in one of the stator parts is energized by single electromagnetic coil and the at least two pairs of magnetic poles in another one of the stator parts is energized by another single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized. When the stator part is magnetized by single electromagnetic coil, a number of electromagnetic coils for the linear motor is minimized.